Ring-fluorinated analogs of various metabolically significant imidazoles have been found to have interesting and useful activities as specific enzyme inhibitors and as antibacterial, antiviral and antileukemic agents. Efforts to expand the variety of analogues to include 2,4-difluoroimidazoles and the isomeric fluoro-aminoimidazoles had been thwarted because of the relative instabilities of these polyfunctional systems. Members of these series containing carboxylic esters or carboxamide at C-5 have now been prepared for biological evaluation. Synthesis of the corresponding ribosides is being explored. Both 2-fluoro-his-TRF and 4-fluoro-his-TRF have been synthesized from the corresponding amino acids. These analogs of the peptide hormones are being evaluated for receptor binding and prolactin release capabilities.